PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 805 



Atmospheric Action. 



The carbonic acid of the air slowly attacks the rocks above the 

 ocean level, and thus turns them to clay, forming carbonates with 

 the soda, potash, lime, and magnesia set free, and carries these 

 down, as carbonates to the sea where the carbonate of soda decom- 

 poses the chlorid of calcium of its waters and forms common salt 

 and carbonate of lime. This series of actions is the source of the 

 salt of the sea, of all clays, and of limestones, which are chemical 

 and not organic in their origin. Organic living .things do not 

 generate the carbonate of lime, but ap])ropriate it, when found for 

 them by chemical reactions ; and thus great portions of our lime- 

 stone rocks are made up of fossil remains. In forty-four feet of 

 limestone there is separated and condensed from the air a whole 

 atmosphere of carbonic acid gas; the early atmosphere was there- 

 fore very dense and unlit for the sustenance of the higher forms 

 of life, until by tar the greater portion of this gas had been 

 removed by the formation of the carbonate of lime and vegetable 

 matter now constituting coal and petroleum. 



The Climate of Early Times. 

 The dense atmosphere of early geologic periods was for the earth 

 like a covering of glass, making for the lower levels a condition 

 of things like an orchard-house in which tropical vegetation flour- 

 ished, even in comparatively northern regions, as we see clearly 

 evidenced by the distribution of organic remains in the various 

 geological formations. Carbonic acid gas jiiixed with our atmos- 

 phere would prevent, to a great extent, the loss of heat by radiation, 

 while oflering but little obstruction to the passage of the suii's 

 heat. 



Granite and other Crystlline Rocks. 



All known rocks are of scdimentar}^ origin, that is, they were 

 deposited from water, and were the result of chemical and mechan- 

 ical action, consisting chieflj^ of limestones, clays and sands, or 

 variable mixtures of these. The infaience of internal heat, aided 

 by Avater, upon these where deeply buried, condensed them and 

 rearranged their particles, changing them into ciystalline rocks, 

 from which the traces of sedimentary origin are nearly eflaced. 

 When again uncovered, these rocks appear as gneiss, mica, slate, or 

 granite. The granitic base or substratum of geology is a fiction. 

 No one has ever seen the primeval crust, which is everywhere 



